/**
 * $RCSfile$
 * $Revision: 2779 $
 * $Date: 2005-09-05 17:00:45 -0300 (Mon, 05 Sep 2005) $
 *
 * Copyright 2003-2006 Jive Software.
 *
 * All rights reserved. Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.jivesoftware.smackx.muc;

import org.jivesoftware.smack.SmackConfiguration;
import org.jivesoftware.smack.packet.Packet;

import java.util.LinkedList;

/**
 * A variant of the {@link org.jivesoftware.smack.PacketCollector} class that
 * does not force attachment to a <code>Connection</code> on creation and no
 * filter is required. Used to collect message packets targeted to a group chat
 * room.
 * 
 * @author Larry Kirschner
 */
class ConnectionDetachedPacketCollector {
	/**
	 * Max number of packets that any one collector can hold. After the max is
	 * reached, older packets will be automatically dropped from the queue as
	 * new packets are added.
	 */
	private int maxPackets = SmackConfiguration.getPacketCollectorSize();

	private LinkedList<Packet> resultQueue;

	/**
	 * Creates a new packet collector. If the packet filter is <tt>null</tt>,
	 * then all packets will match this collector.
	 */
	public ConnectionDetachedPacketCollector() {
		this.resultQueue = new LinkedList<Packet>();
	}

	/**
	 * Creates a new packet collector. If the packet filter is <tt>null</tt>,
	 * then all packets will match this collector.
	 */
	public ConnectionDetachedPacketCollector(int maxSize) {
		this.resultQueue = new LinkedList<Packet>();
		maxPackets = maxSize;
	}

	/**
	 * Polls to see if a packet is currently available and returns it, or
	 * immediately returns <tt>null</tt> if no packets are currently in the
	 * result queue.
	 * 
	 * @return the next packet result, or <tt>null</tt> if there are no more
	 *         results.
	 */
	public synchronized Packet pollResult() {
		if (resultQueue.isEmpty()) {
			return null;
		} else {
			return resultQueue.removeLast();
		}
	}

	/**
	 * Returns the next available packet. The method call will block (not
	 * return) until a packet is available.
	 * 
	 * @return the next available packet.
	 */
	public synchronized Packet nextResult() {
		// Wait indefinitely until there is a result to return.
		while (resultQueue.isEmpty()) {
			try {
				wait();
			} catch (InterruptedException ie) {
				// Ignore.
			}
		}
		return resultQueue.removeLast();
	}

	/**
	 * Returns the next available packet. The method call will block (not
	 * return) until a packet is available or the <tt>timeout</tt> has elapased.
	 * If the timeout elapses without a result, <tt>null</tt> will be returned.
	 * 
	 * @param timeout
	 *            the amount of time to wait for the next packet (in
	 *            milleseconds).
	 * @return the next available packet.
	 */
	public synchronized Packet nextResult(long timeout) {
		// Wait up to the specified amount of time for a result.
		if (resultQueue.isEmpty()) {
			try {
				wait(timeout);
			} catch (InterruptedException ie) {
				// Ignore.
			}
		}
		// If still no result, return null.
		if (resultQueue.isEmpty()) {
			return null;
		} else {
			return resultQueue.removeLast();
		}
	}

	/**
	 * Processes a packet to see if it meets the criteria for this packet
	 * collector. If so, the packet is added to the result queue.
	 * 
	 * @param packet
	 *            the packet to process.
	 */
	protected synchronized void processPacket(Packet packet) {
		if (packet == null) {
			return;
		}
		// If the max number of packets has been reached, remove the oldest one.
		if (resultQueue.size() == maxPackets) {
			resultQueue.removeLast();
		}
		// Add the new packet.
		resultQueue.addFirst(packet);
		// Notify waiting threads a result is available.
		notifyAll();
	}
}
